Screwhead



E. s. HEWITT 2,362,999

SCREW HEAD Nov. 21, 1944.

Filed June 28, 1943 Patented .Nov. 21, 1944 SORIWI-IEAD 'Elmer a... mm, Wilmette, 111. Application June 2a, 194:, Serial No. 492,569

7 Claims. (01. 85-45) This invention which relates generally to screws is concerned particularly with the heads thereof, the objects being to strengthen the construction, improve the connection with the driving bit therefor, and thwart operation [except with a driver which is specially designed for the purpose. Screws having these special features are used in countless places where tampering or malicious removal should be guarded against, and they may be of the wood, machine, drive or other types with heads of any desired contour.

In the description to follow two suggestcd formsoi' screw heads are discussed; also driving bits therefor, as well as an improved hand tool with which any of such bits may be used. As the screws may be produced in a large range of sizes, more than one size of driver will ordinarily be required, so that it becomes desirable to use a single'operating tool to which may be fitted the driving bit best suited for the work in hand.

The screw heads now to be described may be produced for all sizes of screws with sockets of perhaps four sizes only, necessitating four s zes of bits for operation thereof, and perhaps two sizes of each designed to work with two sizes-of bits. A mechanic need therefore carry only two sizes of tools and perhaps four sizes of bits in section being taken on line 3-3 of F g. 12;

' Fig. 4 is, a fragmentary detail in section, taken on line d4 of Fig. 2;

Fig. 5 is an elevational view of a driving b t showing a screw engaging head which is exteriorly knurled;

Fig. 6 is a'similar view, the bit being of larger size and its screw-engaging head being formed exteriorly with circular grooves; v

Fig. 7 which is a view similar to Fig. 2 shows a screw head socket of modified form;

Fig. 8 is a view similar to Fig. 3 showing a. driving bit configured to coact with the screw of Fig.7;

Fig. 9 is a fragmentary longitudinal section of the screw shown in Fig. 7; v

" or easy curving. Rising from the bottom of the Fig. 10 is an elevational view of a hand tool fitted with a removable bit adapted to drive one of the present screws;

Fig. 11 is a transverse section taken on line lI--ll of Fig. 10; and

Fig. 12 is-a detail in longitudinal section taken on line l2--|2 of Fig. 10.

The screw herein illustrated in Figs. l-4 may have a conventional threaded shank S equipped with a head H of any desired contour.- In the head end of the screw is formed an axial socket I 5 having an approximately circular periphery extending through something more than 180, probably around 240", between the points a and b, the socket for the balance of its periphery being eccentrically extended to form a wide lateral recess rbounded by walls that are straight socket is a circular boss l6 coaxial therewith, the height 01' the boss which is shown as a cone being nearly equal to the depth of the socket. At its base the diameter of'the boss is a full half of the diameter of the socket I! at its narrowest point.

In Figs. 7-9 I have shown a screw having a head H, and in the head end of the screw is formed an axial socket 20 bounded by an approximately circular periphery extending through something more than 180, probably around 240, between the points a: and y, the remaining periphery of the socket being fiat in the form of a chord p. A boss 2|, here shown as a cone, rises coaxially from the bottom of the socket to a height which is nearly equal to the depth thereof, the cone diameter at its base being a full half of the diameter of the socket 20 at its narrowest point.

The screw head sockets just described 'ar characterized by an absence of corners, angles or nockets with which an ordinary screw driver blade might engage to apply a rotative force to the screw. Insertion of such a driver into the socket is thwarted by the boss rising from its bottom. Desirably this boss is coned so that if an attempt be made to insert a blade. it will be forced to one side of center. it will en age nothing against which a turning force may be exerted, and it will be cammed outwardly from the socket if rotated therein. For these reasonsv the resent screw. when once set. is immune from tampering except by one having an operating tool that is specially designed for coacting therewith.

An example of such a tool, operable by hand, is illustrated in Fig. 10. As'shown. it comprises a grip 25 of wood, plastic or the like, axially socketed toreceive one end portion of a tube 28 whose opposite walls are slotted longitudinally at 21 for substantially the region that is accommodated within the grip. Fitted crosswise of the tube within the two slots is a plate 28 whose longitudinal edges protrude outwardly beyond the tube exterior to lodge within grooves 29 which may be formed lengthwise along the walls of the grip socket in consequence of the tube, with plate assembled therewith, being driven into the grip, or otherwise. If desired, the plate edges may be formed with ratchet barbs 30 to oppose separation of the tubefrom the grip. By reason of the plate edges being embedded within opposite grooves in the grip socket, the tube is locked non-rotatably in place. A ferrule 3| may be applied over the socketed end of the grip to conceal the presence of the grooves 29.

The opposite tube end which remains exteriorly of the grip is closed by a plug 35 having a nonround socket 35, preferably square in cross section, extending axially to its outer end. To lock the plug against rotation within the tube, a cross pin 31 may be employed. At one point the wall of the plug is provided with a radial passage 38 opening on to its socket, the passage at-its outer end being closed by the surrounding tube. In

this passage is fitted a compression spring 39 exerting opposing thrusts against the closed end of the passage and against a ball 40 which is confined against escape into the socket by a lip 4| which extends peripherally ,of the passage for a distance suflicient to engage the ball while yet permitting it to protrude somewhat into the socket.

A grip in which is fitted such a socketed tube is admirably adapted to receive a driving bit for operation of the present screws. Such a bit, which is shown in two difierent sizes in Figs. 5 and 6, is formed with a body 45 from one end of which is axially extended a non-round shank 46, desirably of square cross section, adapted for snug reception within the plug socket by which it is non-rotatably engaged. In one side of the shank is a lateral socket 41 wherein the protruding ball may engage. This ball acts as a detent to releasably hold the bit in place, permitting a ready exchange of bits when one of different size is to be used. At the end of the bit body, opposite the shank, is formed a screw engaging head 48 having a peripheral contour corresponding with that of the screw head socket with which it is to be used. For the screw of Figs. 1-4 this head in cross section is circular through something more than 180 (about 240, as shown in the: drawing) the balance of its periphery being eccentrically extended to form a lateral boss 49, and the head so formed can be fitted into the screw head socket in only one rotative position, i. e., with the boss occupying the lateral recess 1; and for the screw of Figs. 7-9 the bit head in cross section is circular through something more than 180 (about 240 as shown in the drawing), the balance of its periphery being flattened off as at 50. At its end the head, regardless of its peripheral contour, is formed with an axial socket 5| which desirably is cone-shaped in case the screw-head'bosses are similarly formed.

In use, a bit designed for operation of the screw of Figs. 1-4, when in the single proper rotative position, may be inserted within the head socket preliminary to imparting a turning force to the screw. When so entered, the axial boss IE will be received within the axial socket of the bit,

recessr. The bit is then engaged non-rotatably with the screw. Turning movement of the bit will, through the eccentric boss engagement with the lateral recess, transmit a rotary force to the screw. This results from the fact that the bit is fitted closely within the head socket with insuiilcient clearance remaining for the bit to do more than back away very slightly from the recess toward the socket side which is furthest removed fromthe recess side against which the turning force is being exerted, as indicated clearly in Fig. 4.

It will probably be advantageous to roughen the exterior surface of the work engaging head of the bit throughout the circular portion thereof which is opposite the boss 49. As indicative of two patterns for this, a knurling d is shown as formed in the bit heads of Figs. 5 and 10, and a series of circular ribs 6 on the bit head of Figs. 6 and 12. The reading so formed, which stops short of the eccentric boss 49 or fiat 50 of the bit in each case, tends to bite into the walls of the head socket at thepoints where the thrust force is greatest, thereby establishing therewith a connection which is positive and non-separable as long as the turning force continues. Any such reeding pattern, or others, may be employed to enhance the security of connection between the screw head socket and the operating bit therefor.

A screw produced in accordance with this invention will defy operation by a conventional straight-blade driver, by a coin, or by a thin piece of metal. This results from the fact that the head socket is devoid of any opposite walls, or opposed recesses, upon which such a device must depend for its operative engagement. Furthermore, when the present screw is rotated there is a substantial area of contact, between itself and the bit therefor, as contrasted with the point contact that obtains with the usual slotted screw. Because of this fact the bit tends to remain in the screw head more securely and with no eiiort on the part of the operator, and there is less likelihood of the bit slipping out of place with mutilation of the screw head in consequence. There is also greater strength in the walls surrounding the head socket for withstanding the stresses that result from application of a torsion force consequent upon rotation of the bit. This comes about from the substantial uniformity in the thick walls which surround the socket in the screw head, as well as the continuity of such walls.

I claim:

1. A screw having a head end wherein is an axial socket bounded by an endless wall extending circularly through more than and elsewhere non-circularly to define a lateral recess disposed eccentrically of the screw head.

2. A screw havinga head end wherein is an axial socket bounded by an endless wall extending circularly through more than 180 and elsewhere non-circularly to define a lateral recess disposed eccentrically of the screw head, and a boss extended outwardly from the bottom of the socket.

3. A screw having a head end wherein is an axial socket bounded by an endless wall disposed parallel with the screw axis and continuing circularly through more than 180 and elsewhere non-circularly in a wide are disposed eccentrically of the screw head.

4. A screw having a head end wherein is an axial socket bounded by an endless wall disposed the wall proceeds eccentrically of the socket axis. the socket for a heightslightly .less than the 5. A screw having a head end wherein is an axial socket bounded by an endless. wall disposed parallel with the screw axis and continuing circularly through more than 180 beyond which the wall is extended in a chord.

6. A screw having a head end wherein is an axial socket bounded by an endless wall disposed parallel with the screw axis and continuing through a curve having one radius for a distance of more than 180 and elsewhere in a wide curve but of a lesser radius disposed at a point eccentrically of the single radius curve, the bottom of the socket being relatively flat and transverse to the axis of the screw, and a boss upstanding" from depth thereof. v

97. A screw having a head end wherein is an axial socket formed with a conical boss rising axially from its bottom, the socket being bounded by an endless wall disposed parallel with the screw axis and continuing-througha curvehaving a single radius for more than 180 and elsewhere in a wide curve but of lesser radius disposed at a point eccentrically of the single radius curve, the diameter of the conical boss at its base being at least one-half the diameter of the socket at its narrowest point.

ELMER SPENCER HEWITT. 

